Powered wheelchairs and methods for maintaining a powered wheelchair in a pre-selected position

ABSTRACT

A powered wheelchair includes a seat, a first leg, a second leg, and a control unit. The first leg includes a first inertial measurement unit configured to determine a position of the first leg and a first leg actuator configured to adjust a position of the first leg. The second leg includes a second inertial measurement unit configured to determine a position of the second leg and a second leg actuator configured to adjust a position of the second leg. The control unit is operable to determine a global orientation of the powered wheelchair by averaging the position of first leg and the position of the second leg, and automatically adjusting the position of the first leg with a first leg actuator and the position of the second leg with the second leg actuator based on the global orientation to maintain the seat in a pre-selected position.

TECHNICAL FIELD

The present specification generally relates to powered wheelchairs andmethods and, more specifically, powered wheelchairs and methods formaintaining a seat of a powered wheelchair in a pre-selected position.

BACKGROUND

Powered wheelchairs may generally be navigated by a user manipulating ajoystick or similar user interface device. Oftentimes, as a usertraverses an uneven surface with the powered wheelchair, the user

s center of gravity may shift away from the center of the seat.

Accordingly, a need exists for powered wheelchairs and methods formaintaining a seat of a powered wheelchair in a pre-selected position.

SUMMARY

In embodiments, a powered wheelchair includes a seat, a first leglocated at a first side of the powered wheelchair, a second leg locatedat a second side of the powered wheelchair, and a control unit. Thefirst leg includes a first inertial measurement unit configured todetermine a position of the first leg and a first leg actuatorconfigured to adjust a position of the first leg. The second legincludes a second inertial measurement unit configured to determine aposition of the second leg and a second leg actuator configured toadjust a position of the second leg. The control unit may be operable todetermine a global orientation of the powered wheelchair by averagingthe position of first leg provided by the first inertial measurementunit and the position of the second leg provided by the second inertialmeasurement unit, and automatically adjust the position of the first legwith the first leg actuator and the position of the second leg with thesecond leg actuator based on the global orientation of the poweredwheelchair such that the seat may be maintained in a pre-selectedposition.

In one or more embodiments, a method for maintaining a seat of a poweredwheelchair in a pre-selected position is included. The method includesreceiving, with a control unit, a position of a first leg located at afirst side of the powered wheelchair as determined by a first inertialmeasurement unit. The method further includes receiving, with thecontrol unit, a position of a second leg located at a second side of thepowered wheelchair as determined by a second inertial measurement unit.The method further includes determining, with the control unit, a globalorientation of the powered wheelchair by averaging the position of firstleg provided by the first inertial measurement unit and the position ofthe second leg provided by the second inertial measurement unit. Themethod further includes automatically adjusting, with the control unit,at least one of the first leg of the powered wheelchair and the secondleg of the powered wheelchair with one or more actuators to maintain theseat in the pre-selected position.

These and additional features provided by the embodiments describedherein will be more fully understood in view of the following detaileddescription, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 depicts a side view of a powered wheelchair, according to one ormore embodiments shown and described herein;

FIG. 2 schematically depicts various communicatively coupled modules ofthe powered wheelchair of FIG. 1, according to one or more embodimentsshown and described herein;

FIG. 3A depicts a front view of a wheelchair user making a turningmotion, according to one or more embodiments shown and described herein;and

FIG. 3B depicts a back view of the wheelchair of FIG. 3A, according toone or more embodiments shown and described herein; and

FIG. 3C depicts a top view of the wheelchair of FIG. 3A without theuser, according to one or more embodiments shown and described herein.

DETAILED DESCRIPTION

Embodiments of the present disclosure are directed to poweredwheelchairs and methods for maintaining a seat of the powered wheelchairin a pre-selected position. For example, when a powered wheelchair istraversing uneven terrain, the powered wheelchair may tilt forward,backward, or laterally, thereby shifting a user

s body (e.g., the user

s center of gravity) into an uncomfortable position. The shifting of theuser

s center of gravity may also result in the user falling out of thepowered wheelchair or an overturning of the powered wheelchair. Withthis understanding, the present embodiments are configured to determinea global orientation of the powered wheelchair and to automaticallyadjust the position of one or more legs of the powered wheelchair suchthat the powered wheelchair

s seat is maintained in a pre-selected position. Various embodiments ofpowered wheelchairs and methods for maintaining a seat of a poweredwheelchair in a pre-selected position will be described in more detailherein.

Referring now to FIGS. 1 and 3A-3C, which depict various views of apowered wheelchair 100, according to one or more embodiments shown anddescribed herein. The powered wheelchair 100 may include a seat 102,configured to support a user 200. The powered wheelchair 100 may furtherinclude a first leg 110 located at a first side 104 of the poweredwheelchair 100 and a second leg 120 located at a second side 106 of thepowered wheelchair 100. Each leg 110, 120 may include one or morewheels, e.g., powered via a motor, not shown. For example, in theillustrated embodiment, each leg 110, 120 includes a lower leg linkage116 to which a first wheel 118 and a second wheel 119 are pivotallycoupled such that the first wheel 118 and the second wheel 119 mayrotate to move the powered wheelchair 100 across a surface 170. Thefirst wheel 118 may be coupled to a distal end 126 of the lower leglinkage 116 while the second wheel 119 may be coupled to a proximal end128 of the lower leg linkage 116. The lower leg linkage 116 may bepivotally coupled to an upper leg linkage 117 at the proximal end 128 ofthe lower leg linkage 116. A proximal end 129 of the upper leg linkage117 may be pivotally coupled to the seat 102.

One or more actuators may be configured to move the upper leg linkage117 relative to the lower leg linkage 116 about the proximal end 128 ofthe lower leg linkage 116. For example, the one or more actuators mayinclude a first leg actuator 114 and a second leg actuator 124,schematically illustrated in FIG. 2. The one or more leg actuators 114,124 may include any combination of linear or rotational actuators,configured to adjust the angle of the upper leg linkage 117 in the sideto side and/or the forward to aft directions.

The powered wheelchair 100 may further include a control unit 140, whichwill be more fully described below in relation to FIG. 2. The controlunit may be operable to determine a global orientation of the poweredwheelchair 100 by averaging the position of first leg 110 provided bythe first inertial measurement unit 112 and the position of the secondleg 120 provided by the second inertial measurement unit 122. Thecontrol unit may further be operable to automatically adjust theposition of the first leg 110 and the position of the second leg 120based on the global orientation of the powered wheelchair 100 such thatthe seat 102 of the powered wheelchair 100 may be maintained in apre-selected position.

FIG. 2 schematically depicts various modules of a powered wheelchair100, according to one or more embodiments shown and described herein. Afewer or greater number of modules may be included without departingfrom the scope of the present disclosure. Generally, the poweredwheelchair 100 may include a communication path 130; a control unit 140;one or more actuators 135, which may include a first leg actuator 114, asecond leg actuator 124, and a seat actuator 134; one or more sensingunits 136, which may include a first inertial measurement unit 112, asecond inertial measurement unit 122, one or more force sensing units138, and/or any other sensing units that may output a signal indicativeof the powered wheelchair 100; and one or more user interface devices160.

The communication path 130 provides data interconnectivity betweenvarious modules disposed within the powered wheelchair 100.Specifically, each of the modules can operate as a node that may sendand/or receive data. In one or more embodiments, the communication path130 may include a conductive material that permits the transmission ofelectrical data signals to and between processors, memories, sensors,and valves, pumps, etc. throughout the powered wheelchair 100. Inembodiments, the communication path 130 can be a bus, such as forexample a LIN bus, a CAN bus, a VAN bus, and the like. In furtherembodiments, the communication path 130 may be wireless and/or anoptical waveguide. Components that are communicatively coupled mayinclude components capable of exchanging data signals with one anothersuch as, for example, electrical signals via conductive medium,electromagnetic signals via air, optical signals via optical waveguides,and the like.

The control unit 140 may be configured to selectively operate componentsof the powered wheelchair 100. For example, the control unit 140 maycontrol the first leg actuator 114, the second leg actuator 124, and theseat actuator 134 to automatically adjust the position of the first leg110, the position of the second leg 120, and the position of the seat102 based on the global orientation of the powered wheelchair such thatthe seat 102 of the powered wheelchair 100 may be maintained in apre-selected position. For example, the control unit 140 may include oneor more processors 142 and one or more memory modules 144. The one ormore processors 142 may include any device capable of executingmachine-readable instructions stored on the one or more memory modules.Accordingly, each processor may include a controller, an integratedcircuit, a microchip, a computer, and/or any other computing device. Itis noted that the one or more processors 142 may reside within thepowered wheelchair 100 and/or external to the powered wheelchair 100.

The one or more memory modules 144 may be communicatively coupled to theone or more processors 142 over the communication path 130. The one ormore memory modules 144 may be configured as volatile and/or nonvolatilememory and, as such, may include random access memory (including SRAM,DRAM, and/or other types of RAM), flash memory, secure digital (SD)memory, registers, compact discs (CD), digital versatile discs (DVD),and/or other types of non-transitory computer-readable mediums.Depending on the particular embodiment, these non-transitorycomputer-readable mediums may reside within the powered wheelchair 100and/or external to the powered wheelchair 100.

Embodiments of the present disclosure include logic stored on the one ormore memory modules 144 that includes machine-readable instructionsand/or an algorithm written in any programming language of anygeneration (e.g., 1GL, 2GL, 3GL, 4GL, and/or 5GL) such as, machinelanguage that may be directly executed by the one or more processors142, assembly language, obstacle-oriented programming (OOP), scriptinglanguages, microcode, etc., that may be compiled or assembled intomachine readable instructions and stored on a machine readable medium.Similarly, the logic and/or algorithm may be written in a hardwaredescription language (HDL), such as logic implemented via either afield-programmable gate array (FPGA) configuration or anapplication-specific integrated circuit (ASIC), and their equivalents.Accordingly, the logic may be implemented in any conventional computerprogramming language, as pre-programmed hardware elements, and/or as acombination of hardware and software components. As will be described ingreater detail herein, logic stored on the one or more memory modules144 allows the control unit 140 to, for example, to determine a globalorientation of the powered wheelchair 100 by averaging the position offirst leg 110 provided by the first inertial measurement unit 112 andthe position of the second leg 120 provided by the second inertialmeasurement unit 122, and automatically adjust the position of the firstleg 110, the position of the second leg 120, and the position of theseat 102 based on the global orientation of the powered wheelchair 110such that the seat 102 may be maintained in a pre-selected position.

The first and second leg actuators 114, 124 and the seat actuator 134may be communicatively coupled to the control unit 140 over thecommunication path 130. As will be described below, the control unit 140may execute logic to control a position of the first and second legactuators 114, 124 to automatically adjust the position of the first leg110 and the position of the second leg 120 based on the globalorientation of the powered wheelchair 100 such that the seat 102 may bemaintained in a pre-selected position.

The one or more sensing units 136 are communicatively coupled to thecontrol unit 140 over the communication path 130. The first inertialmeasurement unit 112 and the second inertial measurement unit 122 mayinclude any sensing units configured to output a position of the firstleg 110 and the second leg 120, respectively. For example, the first andsecond inertial measurement units 112, 122 may include a combination ofone or more gyroscopes and one or more accelerometers. As such, thefirst inertial measurement unit 112 and the second inertial measurementunit 122 may indicate that the powered wheelchair 100 is traveling overan uneven surface 170 based on the tilt of the first leg 110 and thesecond leg 120, respectively. However, it should be understood that thefirst and second inertial measurement units 112, 122 are not limited toany particular type of inertial measurement unit.

FIGS. 3A-3C illustrate a powered wheelchair 100 traveling over an unevensurface 170. FIG. 3A depicts a front view of the powered wheelchair 100with a user 200 positioned within the seat. FIG. 3B depicts a back viewof the powered wheelchair 100 with the user 200 removed. FIG. 3C depictsa top or aerial view of the powered wheelchair 100 with the user 200removed.

Referring to FIG. 3B, the first inertial measurement unit 112 may bemounted to or within the first leg 110 of the powered wheelchair 100 andthe second inertial measurement unit 122 may be mounted to or within thesecond leg 120 of the powered wheelchair 100. The control unit 140 mayreceive a signal from the first inertial measurement unit 112 todetermine the position of the first leg 110 of the powered wheelchair.The control unit 140 may further receive a signal from the secondinertial measurement unit 122 to determine the position of the secondleg 120. Accordingly, the control unit 140 may determine a globalorientation of the powered wheelchair by averaging the position of thefirst leg 110 provided by the first inertial measurement unit 112 andthe position of the second leg 120 provided by the second inertialmeasurement unit 122. Based on the determination of the globalorientation of the powered wheelchair 100, the control unit mayautomatically adjust the position of the first leg 110 and the positionof the second leg 120 with the first and second leg actuators 114, 124,respectively, such that the seat 102 may be maintained in a pre-selectedposition, regardless of the pitch or tilt of the uneven surface 170.

In embodiments, the control unit 140 determines the global orientationof the powered wheelchair 100 by aggregating tilt (e.g., forward tilt)data and roll (e.g., lateral tilt) data provided by the first inertialmeasurement unit 112 and the second inertial measurement unit 122. Theseat 102 may further include a third inertial measurement unit 108configured to confirm that the seat 102 may be being maintained in thepre-selected position. If the third inertial measurement unit 108 sensesthat the seat 102 is not maintained in the pre-selected position, thethird inertial measurement unit 108 may command the control unit 140 tostop movement of the powered wheelchair 100 or provide a signal to theuser 200 that the powered wheelchair is not functioning properly and/oris in need of servicing.

In one or more embodiments, the first leg actuator 114 may be configuredto adjust at least one of a height, a pitch, and a roll of the first leg100. Likewise, the second leg actuator 124 may be configured to adjustat least one of a height, a pitch, and a roll of the second leg 120.Together, the first and second leg actuators 114, 124 may maintain theseat 102 in the pre-selected position, regardless of tilt or pitch ofthe uneven surface 170. For example, the user 200 may define apre-selected position for the seat 102 at 0.6 meters (m). Therelationship between the pre-selected position (0.6 m) and hip and kneeangles of the user 200 may be defined by Equation (1):

$\begin{matrix}{{H(h)} = {\left( \frac{1}{\alpha} \right)\left( {h - \beta} \right)}} & {{Equation}\mspace{14mu}(1)}\end{matrix}$

where α and β are representative constants selected by the manufacturerof the powered wheelchair 100. As a non-limiting example, α=0.0102 andβ=0.3456, such that H(0.6)=˜25°. In other words, the first and secondleg actuators 114, 124 maintain the first and second legs 110, 120 at anoffset of 25°.

In a first example, assume that the user 200 is traveling in the poweredwheelchair 100 over an uneven surface with a pitch angle of −10° and aroll angle of 0°. In this scenario, the first internal measurement unit112 may measure a Pitch₁ of −10° and a Roll′ of 0° for the first leg 110of the powered wheelchair 100. Likewise, the second internal measurementunit 122 may measure a Pitch₂ of −10° and a Roll₂ of 0° for the secondleg 120 of the powered wheelchair 100. This pitch and roll data may bethen sent to the control unit 140 which may be capable of determiningthe global position of the powered wheelchair 100 with Equations (2) and(3):

$\begin{matrix}{P = {\frac{{Pitch1} + {Pitch2}}{2} = {\frac{{- 10} - 10}{2} = {{- 10}{^\circ}}}}} & {{Equation}\mspace{14mu}(2)} \\{R = {\frac{{Roll1} + {Roll2}}{2} = {\frac{0 + 0}{2} = {0{^\circ}}}}} & {{Equation}\mspace{14mu}(3)}\end{matrix}$

Based on this determination, the control unit 140 may command the firstand second leg actuators 114, 124 to provide a pitch correction of −10°to the seat 102, which accounts for the pitch angle of the unevensurface, by adjusting the first and second legs 110, 120, respectively,to maintain the seat 102 in the pre-selected position.

In a second example, assume that the user 200 is traveling in thepowered wheelchair 100 over an uneven surface with a roll angle of −5°and a pitch angle of 0°. In this scenario, the first internalmeasurement unit 112 measures a Pitch₁ of 0° and a Roll′ of −5° for thefirst leg 110 of the powered wheelchair 100. Likewise, the secondinternal measurement unit 122 measures a Pitch₂ of 0° and a Roll₂ of −5°for the second leg 120 of the powered wheelchair 100. This pitch androll data may be sent to the control unit 140 which may be capable ofdetermining the global position of the powered wheelchair 100 withEquations (2) and (3):

$\begin{matrix}{P = {\frac{{Pitch1} + {Pitch2}}{2} = {\frac{0 + 0}{2} = {0{^\circ}}}}} & {{Equation}\mspace{14mu}(2)} \\{R = {\frac{{Roll1} + {Roll2}}{2} = {\frac{{- 5} - 5}{2} = {{- 5}{^\circ}}}}} & {{Equation}\mspace{14mu}(3)}\end{matrix}$

Based on this determination, the control unit 140 may command the firstand second leg actuators 114, 124 to provide a roll correction of −5° tothe seat 102, which accounts for the pitch angle and roll angles of theuneven surface, by adjusting the first and second legs 110, 120,respectively, to maintain the seat 102 in the pre-selected position.

In a third example, assume that the user 200 is traveling in the poweredwheelchair 100 over an uneven surface with a pitch angle and a rollangle that is different for each of the first and second legs 110, 120.In this scenario, the first internal measurement unit 112 may measure aPitch₁ of −10° and a Roll₁ of −4° for the first leg 110 of the poweredwheelchair 100. Likewise, the second internal measurement unit 122 maymeasure a Pitch₂ of −6° and a Roll₂ of −8° for the second leg 120 of thepowered wheelchair 100. This pitch and roll data may be sent to thecontrol unit 140 which may be capable of determining the global positionof the powered wheelchair 100 with Equations (2) and (3):

$\begin{matrix}{P = {\frac{{Pitch1} + {Pitch2}}{2} = {\frac{{- 10} - 6}{2} = {{- 8}{^\circ}}}}} & {{Equation}\mspace{14mu}(2)} \\{R = {\frac{{Roll1} + {Roll2}}{2} = {\frac{{- 4} - 8}{2} = {{- 6}{^\circ}}}}} & {{Equation}\mspace{14mu}(3)}\end{matrix}$

Based on this determination, the control unit 140 may command the firstand second leg actuators 114, 124 to provide a pitch correction of −8°and a roll correction of −5° to the seat 102, which accounts for thepitch and roll angles of the uneven surface, by adjusting the first andsecond legs 110, 120, respectively, to maintain the seat 102 in thepre-selected position.

Referring to FIG. 3C, the one or more force sensors 138 may be mountedto one or more of the seat 102, a headrest 141, arm rests 143, a backsupport 145, a lower leg and foot rest 147, or any combination thereofand output a force signal. The control unit 140 may receive the forcesignal of the one of the one or more force sensors 138 to determine thecenter of gravity of the user 200 and/or determinate how the user 200 issitting in the chair (e.g., leaning forward, reclining, leaning on thearm rests 143, etc.). Accordingly, the control unit 140 may also detectchanges in the user

s 200 posture or center of gravity based on the one or more forcesensors 138. In embodiments, changes to the user

s 200 posture or center of gravity may cause the control unit 140 tooperate the first leg actuator 114, the second leg actuator 124, theseat actuator 134, or any combination thereof, to adjust the user sposture or center of gravity to a preferred position (e.g., the centerof the seat 102 or some other pre-selected position).

The pre-selected position of the seat 102 of the powered wheelchair 100may be based on one or more factors including but not limited to, apredetermined leaning constant, the speed and/or acceleration of thepowered wheelchair 100, a body morphology of the user 200,characteristics of the powered wheelchair 100 (e.g., height, weight,etc.), and/or one or more user preferences. For example, thepre-selected position of the seat 102 may be a predetermined angle θrelative to a horizontal plane. In embodiments, the pre-selectedposition of the seat 102 may be a substantially horizontal position. Forexample, the seat 102 may be maintained within 5° of the pre-selectedposition (e.g., the substantially horizontal position).

It is noted that the speed and/or acceleration (or deceleration) of thepowered wheelchair 100 may also affect the position of the seat 102.Accordingly, in some embodiments, the inertial measurement units 112,122 may be configured to output an acceleration and/or speed signalindicative of the acceleration and/or speed of the powered wheelchair100. Based on the speed or acceleration signal, the control unit 140 maydetermine a speed or acceleration of the powered wheelchair 100. In someembodiments, the control unit 140 may the adjust the first leg 110(e.g., with the first leg actuator 114) and/or the second leg 120 (e.g.,with the second leg actuator 124) based on the speed or acceleration ofthe powered wheelchair 100.

As noted herein, user information, preference information, or the likemay be communicated to control unit 140 using the one or more userinterface devices 160. That is the one or more user interface devices160 may be communicatively coupled to the control unit 140 over thecommunication path 130. The one or more user interface devices 160 mayinclude any combinations of joysticks, knobs, buttons, touchscreens,keyboards, microphones, or the like, which allow the user 200 tointeract with the control unit 140. As noted above, the user 200 mayindicate via the one or more user interface devices 160 one or morepreferences (e.g., posture preferences, leaning preferences, or thelike) which may be used in determining the pre-selected position of theseat 102. In some embodiments, the user 200 may provide informationregarding the user

s body morphology (e.g., weight, height, missing limbs, etc.) to allowthe control unit 140 to tune calculations of the pre-selected positionto the user

s particular body characteristics. Accordingly, the control unit 140 mayreceive the one or more user preferences and/or characteristicinformation from the one or more user interface devices 160 and tailorthe pre-selected position of the seat 102 based on the users preferencesand/or the user s characteristic information.

A method for maintaining a seat of the powered wheelchair 100 in apre-selected position is also described below. It is noted that while anumber of steps are described, a fewer or greater number of steps, inany order, may be included.

The method may include receiving, with the control unit 140, a positionof the first leg 110 as determined by the first inertial measurementunit 112 and a position of the second leg 120 a determined by the secondinertial measurement unit 122. The method may further includedetermining, with the control unit 140, a global orientation of thepowered wheelchair 100 by averaging the position of first leg 110provided by the first inertial measurement unit 110 and the position ofthe second leg 120 provided by the second inertial measurement unit 122.The method may further include automatically adjusting, with the controlunit 140, at least one of the first leg 110 of the powered wheelchair100 and the second leg 120 of the powered wheelchair 100 to maintain theseat 102 in the pre-selected position. The method may further includeconfirming the pre-selected position of the seat 102 with a thirdinertial measurement unit 108. Accordingly, the control unit 140 maydynamically respond to changes in the position of the first leg 100and/or the second leg 120 caused by traversing an uneven surface 170 tomaintain the seat 102 in the pre-selected position.

It should now be understood that embodiments of the present disclosureare directed to powered wheelchairs and methods for maintaining a seatof a powered wheelchair in a pre-selected position. For example, when apowered wheelchair is traversing uneven terrain, the seat of the poweredwheelchair may tilt. The tilting may influence a user

s center of gravity that may result in overturning of the poweredwheelchair. Embodiments of the present disclosure, therefore, areconfigured to determine the position of the legs of the poweredwheelchair and further to determine a global orientation of the poweredwheelchair by averaging the position of the first leg provided by afirst inertial measurement unit and the position of the second legprovided by the inertial measurement unit. Based on determining theglobal orientation of the powered wheelchair, the position of the firstleg and the position of the second leg may be automatically adjustedsuch that the powered wheelchair

s seat is maintained in a pre-selected (e.g., substantially horizontal)position). The pre-selected position may also take into account forvarious factors, which may be inputted by a user of the poweredwheelchair with a user interface device.

It is noted that the terms

substantially

and

about

may be utilized herein to represent the inherent degree of uncertaintythat may be attributed to any quantitative comparison, value,measurement, or other representation. These terms are also utilizedherein to represent the degree by which a quantitative representationmay vary from a stated reference without resulting in a change in thebasic function of the subject matter at issue.

While particular embodiments have been illustrated and described herein,it should be understood that various other changes and modifications maybe made without departing from the spirit and scope of the claimedsubject matter. Moreover, although various aspects of the claimedsubject matter have been described herein, such aspects need not beutilized in combination. It is therefore intended that the appendedclaims cover all such changes and modifications that are within thescope of the claimed subject matter.

What is claimed is:
 1. A powered wheelchair comprising: a seat; a firstleg located at a first side of the powered wheelchair, the first legcomprising a first inertial measurement unit configured to determine aposition of the first leg and a first leg actuator configured to adjusta position of the first leg; a second leg located at a second side ofthe powered wheelchair, the second leg comprising a second inertialmeasurement unit configured to determine a position of the second legand a second leg actuator configured to adjust a position of the secondleg; and a control unit operable to: determine a global orientation ofthe powered wheelchair by averaging the position of the first legprovided by the first inertial measurement unit and the position of thesecond leg provided by the second inertial measurement unit; andautomatically adjust the position of the first leg with the first legactuator and the position of the second leg with the second leg actuatorbased on the global orientation of the powered wheelchair such that theseat is maintained in a pre-selected position.
 2. The powered wheelchairof claim 1, further comprising a third inertial measurement unitconfigured to confirm that the seat is being maintained in thepre-selected position.
 3. The powered wheelchair of claim 1, wherein thethird inertial measurement unit is located at the seat of the poweredwheelchair.
 4. The powered wheelchair of claim 1, wherein the controlunit determines the global orientation of the powered wheelchair byaggregating forward tilt data and lateral tilt data provided by thefirst inertial measurement unit and the second inertial measurementunit.
 5. The powered wheelchair of claim 1, further comprising a userinterface device communicatively coupled to the control unit, whereinthe control unit is configured to receive one or more user preferenceswith the user interface device, the one or more user preferencescomprising at least the pre-selected preference.
 6. The poweredwheelchair of claim 5, wherein the pre-selected preference is such thatthe seat is in a substantially horizontal position.
 7. The poweredwheelchair of claim 1, wherein the seat is maintained within 5° of thepre-selected position.
 8. The powered wheelchair of claim 1, furthercomprising one or more force sensors configured to cause the controlunit to operate the first leg actuator, the second leg actuator, a seatactuator, or any combination thereof to maintain the seat in thepre-selected position.
 9. The powered wheelchair of claim 1, wherein:the first leg actuator is configured to adjust at least one of a height,a pitch, and a roll of the first leg; and the second leg actuator isconfigured to adjust at least one of a height, a pitch, and a roll ofthe second leg.
 10. The powered wheelchair of claim 1, wherein: thecontrol unit is operable to determine an acceleration of the poweredwheelchair based on an acceleration signal of the first inertialmeasurement unit, the second inertial measurement unit, or both thefirst inertial measurement unit and the second inertial measurementunit; and the pre-selected position is based on the acceleration of thewheelchair.
 11. A method for maintaining a seat of a powered wheelchairin a pre-selected position, the method comprising: receiving, with acontrol unit, a position of a first leg located at a first side of thepowered wheelchair as determined by a first inertial measurement unit;receiving, with the control unit, a position of a second leg located ata second side of the powered wheelchair as determined by a secondinertial measurement unit; determining, with the control unit, a globalorientation of the powered wheelchair by averaging the position of firstleg provided by the first inertial measurement unit and the position ofthe second leg provided by the second inertial measurement unit; andautomatically adjusting, with the control unit, at least one of thefirst leg of the powered wheelchair and the second leg of the poweredwheelchair with one or more actuators to maintain the seat in thepre-selected position.
 12. The method of claim 11, further comprisingconfirming the pre-selected position of the seat with a third inertialmeasurement unit.
 13. The method of claim 12, wherein the third inertialmeasurement unit is located at the seat of the powered wheelchair. 14.The method of claim 11, wherein determining the global orientation ofthe powered wheelchair comprises aggregating, with the control unit,forward tilt data and lateral tilt data provided by the first inertialmeasurement unit and the second inertial measurement unit.
 15. Themethod of claim 11, further comprising receiving, with the control unit,one or more user preferences with from one or more user interfacedevices, the one or more user preferences comprising at least thepre-selected preference.
 16. The method of claim 15, wherein thepre-selected preference is such that the seat is in a substantiallyhorizontal position.
 17. The method of claim 11, wherein the seat ismaintained within 5° of the pre-selected position.
 18. The method ofclaim 11, wherein the powered wheelchair comprises one or more forcesensors configured to cause the control unit to operate the first legactuator, the second leg actuator, a seat actuator, or any combinationthereof to maintain the seat in the pre-selected position.
 19. Themethod of claim 18, wherein: the first leg actuator is configured toadjust at least one of a height, a pitch, and a roll of the first leg;and the second leg actuator is configured to adjust at least one of aheight, a pitch, and a roll of the second leg.
 20. The method of claim11, further comprising: receiving, with the control unit, anacceleration signal from the first inertial measurement unit, the secondinertial measurement unit, or both the first inertial measurement unitand the second inertial measurement unit; and determining anacceleration of the powered wheelchair based on the acceleration signal,wherein the pre-selected position is based on the acceleration of thewheelchair.